Power transmission device

Abstract

A power transmission device has a first clutch member 4a coupled to an output member 3. A second clutch member 4b has a plurality of driven-side clutch plates 7. A back-torque transmitting cam presses the drive-side clutch plates 6 and the driven-side clutch plates 7 against each other by moving the second clutch member 4b when a rotational force is input to the first clutch member 4a. A cushioning member 12 is interposed between the first clutch member 4a and the second clutch member 4b. The cushioning member 12, by being compressed, applies an urging force while allowing movements of an interlocking member 9 and a pressure member 5 in a process where the interlocking member 9 moves and the pressure member 5 moves from the inactive position toward the active position.

What is claimed is: 
     
       1. A power transmission device comprising:
 a clutch housing rotating together with an input member rotated by engine driving power of a vehicle and including a plurality of drive-side clutch plates; 
 a clutch member including a plurality of driven-side clutch plates formed alternately with the drive-side clutch plates of the clutch housing and the clutch member coupled to an output member capable of rotating a wheel of the vehicle; 
 a pressure member movable between an active position and an inactive position, in the active position, the pressure member presses the drive-side clutch plates and the driven-side clutch plates against each other to be able to transmit the driving power of the engine to the wheel and in the inactive position, the pressure member releases a press-contact force between the drive-side clutch plates and the driven-side clutch plates to be able to stop transmitting the driving power of the engine to the wheel; 
 a weight member disposed in a groove portion extending in a radial direction of the clutch housing and movable from a radially-inner position to a radially-outer position in the groove portion due to a centrifugal force generated as the clutch housing rotates; 
 an interlocking member moving the pressure member from the inactive position to the active position as the weight member moves from the radially-inner position to the radially-outer position; 
 a release spring holding the pressure member at the inactive position, the release spring is compressed as the interlocking member moves and the pressure member moves from the inactive position toward the active position, and the release spring applying an urging force while allowing movements of the interlocking member and the pressure member until the drive-side clutch plates and the driven-side clutch plates reach an engaged state before the drive-side clutch plates and the driven-side clutch plates are pressed against each other; and 
 a clutch spring configured to be compressed in a process where the interlocking member moves after the drive-side clutch plates and driven-side clutch plates have reached the engaged state and the clutch spring applies a press-contact force between the drive-side clutch plates and the driven-side clutch plates while allowing movement of the interlocking member, 
 the clutch member includes 
 a first clutch member coupled to the output member, 
 a second clutch member attached to the driven-side clutch plates; and 
 a back-torque transmitting cam pressing the drive-side clutch plates and the driven-side clutch plates against each other by moving the second clutch member when a rotational force is input to the first clutch member via the output member, 
 a cushioning member interposed between the first clutch member and the second clutch member, the cushioning member configured to be, by being compressed, applying an urging force while allowing movements of the interlocking member and the pressure member in a process where the interlocking member moves and the pressure member moves from the inactive position toward the active position. 
 
     
     
       2. The power transmission device according to  claim 1 , wherein the cushioning member includes a spring that is set to a load such that the spring is compressed before the clutch spring starts to be compressed. 
     
     
       3. The power transmission device according to  claim 1 , wherein the cushioning member is accommodated in an accommodation recessed portion that is formed in a surface where the first clutch member and the second clutch member face each other. 
     
     
       4. The power transmission device according to  claim 3 , wherein the accommodation recessed portion includes an annular groove, and the cushioning member includes a spring with an annular shape conformed to a shape of the groove. 
     
     
       5. The power transmission device according to  claim 4 , wherein the back-torque transmitting cam is formed in a plurality of annular shapes in the surface where the first clutch member and the second clutch member face each other, and the accommodation recessed portion is formed in a concentric circular shape at a position that is adjacent to the back-torque transmitting cam.